Hind-Limb Collateral Ligament Injuries Examined

Severe hind-limb lameness in horses has many possible causes, including collateral ligament desmitis of the hock.

Photo: Anne M. Eberhardt/The Horse

Severe hind-limb lameness in horses has many possible causes, including collateral ligament desmitis of the hock.

To better understand the effects of this injury, researchers at Oklahoma’s Oakridge Equine Hospital and Texas A&M’s College of Veterinary Medicine completed a study that traced 12 horses presenting with synovitis (inflammation of the synovial lining inside the joint) in the hock and evidence of collateral ligament desmitis on ultrasound over an eight-year period.

Collateral ligament desmitis (inflammation of the collateral ligament, which is located on either side of most joints) often develops as a result of a ligament sprain or strain. The collateral ligament in the hock runs adjacent to the hock's joint capsule, providing connectivity and stability to the joint. Damage to the structure can occur due to tearing of the joint capsule, cartilage damage to the joint, or bone chips.

Lead researcher Lauren Lamb, DVM, Dipl. ACVS, of Texas A&M, and his team reported that each horse in this study presented with swelling around the hock, accompanied by severe lameness, and was hospitalized for an average of six-and-a-half days. Eight of the 12 horses underwent arthroscopic surgery to flush the joint and remove injured tissue, torn cartilage, or bone fragments.

Additionally, the majority of the horses received systemic antibiotics to lessen the risk of sepsis development (a systemic inflammatory response syndrome in which the whole body is in an inflammatory state due to the presence of a known or suspect bacterial infection).

Veterinarians also used a variety of other treatments to combat the injuries, including DMSO sweat wraps in all horses; shock wave therapy in three horses; flushing of and dead tissue removal from the tarsosocrural joint, (located between the tibia and the talus in the upper joint of the hock) in eight horses; interarticular antibiotics in six horses; regional limb perfusions; and a second arthroscopic surgery to remove additional tissue and cartilage in two horses.

All horses were discharged with instructions for limited turnout/walking schedules and follow-up appointments for ultrasounds over the next three to six months. Of the study horses:

Only four returned to their previous use at the time of follow-up (which was an average of five-and-a-half years after the initial diagnosis);

Six were pasture sound at time of follow-up, underscoring the potential long-term effects of such injuries;

One was still on layup; and

Another had been euthanized due to persistent severe lameness in the affected leg one month after treatment.

The team noted these results indicated affected horses have a guarded prognosis to return to athletic soundness.

The team surprisingly found that many of the cases (nine of the 12) sustained their initial injuries either in a stall or while turned out in a pasture, Lamb said. However, that the sample size in this study was relatively small, so these results don’t necessarily mean that stall accidents resulting in collateral ligament damage are common, he added.

To avoid collateral ligament injuries while working your horse, Lamb suggests owners ensure the horse is “working on good footing, shod properly, and well-conditioned.”

As for avoiding injuries in horses that are turned out or at rest in the stall, he said no perfect solutions to prevent all injuries exist, as most horse owners know all too well.

If your horse does sustain a hind-leg injury, Lamb advises owners have a veterinarian assess the degree of lameness and swelling right away, as significant swelling and lameness in the hock can indicate a collateral ligament injury.

About the Author

Natalie Voss is a freelance writer and editor based in Kentucky. She received her bachelor's degree in equine science from the University of Kentucky and has worked in public relations for equine businesses and organizations. She spends her spare time riding her Draft cross, Jitterbug.

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